The present invention relates to an iron core winding, which is applicable to a stator iron core and a rotor iron core, and a variable reluctance angle detector that uses the iron core winding. Such an angle detector is widely used in devices that require alignment, such as a variety of robots and FA devices. In particular, the present invention relates to a variable reluctance angle detector that includes an iron core. A winding of the iron core is coiled with full turns, and an output winding that uses the iron core winding is coiled with the same winding number on each tooth. The shape of the rotor is formed to induce voltage in a sinusoidal manner.
In the past, detectors such as a resolver or a synchro have had a predetermined output signal form (primarily a sine wave or a cosine wave). For example, referring to FIG. 11, published Japanese patent application No. 06-229780 (which corresponds to U.S. Pat. No. 5,486,731) shows a detector in which winding groups x, which are coiled in series, are serially connected. The windings x are sequential and are formed at every slot 30. A group y of the winding groups x is constructed for each phase. In order to obtain a magnetic flux distribution according to a sine wave, a sine wave value is found for the winding number of each slot. The total winding number is divided by the value of the sine wave for each slot position.
As shown in FIG. 11, there are ten slots 30 of the ring-shaped core 29. That is, S=10. There are ten teeth 31. The winding group for one phase of the two-phase pole resolver is y. The winding group y for one phase is formed by ten of the winding groups x. The number of winding groups x is S. By forming n of the single-phase winding groups y, an n-phase winding group Z is formed. By forming the n-phase winding group Z for the entire circumference (2n radians) of the annular core 29, a pulse like magnetomotive force is generated as indicated by the bar graph of FIG. 11 for each winding group x. Note that the winding differs depending on the slot 30. When each magnetomotive force is connected with an approximation line, as shown in FIG. 11, the magnetic flux appears as a sine wave A.
The general formulas for the n-phase winding group Z, in which the winding groups x are serially connected are as follows:
            N              k        ⁢                                  ⁢        1              =                  W        ⁢                                  ⁢                  sin          ⁡                      [                          2              ⁢              π              ⁢                                                          ⁢                              P                /                S                            ⁢                              {                                                      (                                          k                      -                      1                                        )                                    +                                      1                    2                                                  }                                      ]                                                            ∑                          i              =              1                        S                    ⁢                      sin            ⁡                          [                              2                ⁢                π                ⁢                                                                  ⁢                                  P                  /                  S                                ⁢                                  {                                                            (                                              i                        -                        1                                            )                                        +                                          1                      2                                                        }                                            ]                                      ⁢                                                  N              k        ⁡                  (          n          )                      =                  W        ⁢                                  ⁢                  sin          ⁡                      [                                          2                ⁢                π                ⁢                                                                  ⁢                                  P                  /                  S                                ⁢                                  {                                                            (                                              k                        -                        1                                            )                                        +                                          1                      2                                                        }                                            +                                                2                  ⁢                                      π                    ⁡                                          (                                              n                        -                        1                                            )                                                                      n                                      ]                                                            ∑                          i              =              1                        S                    ⁢                      sin            ⁡                          [                                                2                  ⁢                  π                  ⁢                                                                          ⁢                                      P                    /                    S                                    ⁢                                      {                                                                  (                                                  i                          -                          1                                                )                                            +                                              1                        2                                                              }                                                  +                                                      2                    ⁢                                          π                      ⁡                                              (                                                  n                          -                          1                                                )                                                                              n                                            ]                                      ⁢                                      where Nk(n) is the number of turns of the winding portion at the kth slot, k is an integer between 1 and S, in the nth winding group in the n-phase, i is a counter for the summation, W is the total number of turns (the sum of the windings wound at each slot of i=1 through S in one phase).
Referring to FIG. 12, published Japanese patent application 08-178611 (which corresponds to U.S. Pat. No. 5,757,182) shows another angle detector. In this example, in order to create a sinusoidal induced voltage distribution at the output winding for one phase, the output winding is distributed in a sine wave form.
In the variable reluctance angle detector of FIG. 12, the rotor has a form such that its gap permeance varies with angle θ in the manner of a sine wave. The structure includes an iron core. The number of poles of the excitation winding is the same as the number of slots. The output winding is coiled so that the distribution of the induced voltage generated at the output winding, for one phase, corresponds to a sine wave. The sine output winding 36 and the cosine output winding 37 are coiled with a one-slot pitch (no slot is skipped and the coils are connected in series). The electric angle between the sine output winding 36 and the cosine output winding 37 is ninety degrees. The windings are distributed such that the number (volume) of windings follows a sine wave distribution, so that each induced voltage distribution is sinusoidal. The number of windings for each of the output windings 36 and 37 is the number of turns that is proportional to sin θ for the sine winding and cos θ for the cosine winding, and the polarity of a given winding is determined according to the polarity of the sine output voltage 38 and cosine output voltage 39, by taking into account the polarity of the excitation winding 40.
In the stator windings shown in the two prior art documents discussed above, the winding groups are serially connected. Therefore, as shown in FIG. 5, the polarity of the magnetic poles is switched from magnetic pole 21 to magnetic pole 25. If the magnetic pole 21 is reversely wound, or wound counterclockwise (CCW) in a left-hand winding, the winding at the entrance, or beginning, and the winding at the exit, or end, cross. Thus, complete, fully-rounded coils are formed, and the required number of windings corresponds to the number of coils formed. The conventional winding method of FIG. 5 is shown for the purpose of comparison with the winding method of the present invention.
The crossover segment 212W, from winding 21W of the first magnetic pole 21, leads to a right-handed coil in the clockwise direction (CW) on the next magnetic pole 22 to form winding 22W. Winding 22W is further coiled so that it extends towards the next magnetic pole 23. Therefore, as shown, a gap with a dimension p is formed between the beginning and end of the winding 22W, and the final coil is not a complete, fully-rounded coil, as shown.
The crossover segment 223W that extends from the winding 22W is a left handed coil in the counterclockwise direction (CCW) on magnetic pole 23 to form winding 23W. Winding 23W is further coiled so that it extends toward the next magnetic pole 24. Therefore, like the first winding 21W, the third winding 23W is formed by complete, fully rounded coils, and the required number of windings corresponds to the number of coils formed.
The crossover segment 234W that extends from the winding 23W is a right handed coil in the clockwise direction (CW) on the next magnetic pole 24 to form winding 24W. Winding 24W is further coiled so that it extends towards the next magnetic pole 25. Therefore, a gap with a dimension p is formed, and the last coil is not fully-rounded and complete.
Next, the cross-over segment 245W that extends from the winding 24W is a left handed coil in the counterclockwise direction (CCW) on the magnetic pole 25 to form a winding 25W. The winding 25W is further coiled so that it extends toward the next magnetic pole. Therefore, as in the case of the first magnetic pole 21, winding 25W is formed by fully-rounded coils, and the required number of windings corresponds to the number of coils.
In the published Japanese patent application No. 06-229780, in order to obtain a sine wave magnetic flux distribution, a sine wave value is found for the winding number for each slot of the single-phase winding group, and the total winding number is divided by the value of the sine wave for each position of the slot. In published Japanese patent application 08-178611, in order to set the induced voltage distribution at the output winding for one phase to be a sine wave distribution, the output winding is coiled while being distributed at one slot pitch for each slot and distributed in a sine wave form. Therefore, in the prior art examples, the greater the number of turns in an output winding, the farther the output winding is from the corresponding magnetic pole. Thus, the correspondence between the magnetic flux distribution generated by the winding group for one phase and a sine wave is less accurate. Consequently, in practical use, the prior art devices often require adjustment. In addition, making the induced voltage distribution correspond to a sine wave distribution is also difficult and it often requires adjustment during practical use.
Furthermore, in the prior art examples, since the number of windings of the output winding is required to be distributed in correspondence to a sine wave, when the maximum number of windings of the winding group is coiled around a specific magnetic pole, the number of windings of other poles becomes less than the maximum number of windings. Therefore, the induced voltage of the output winding is reduced to a small value. Consequently, the induced voltage output for each winding group becomes small, and it is difficult to create intervals given the noise level.
When the maximum number of windings is further increased to maintain a large dynamic range by increasing the intervals with the noise level, the output winding is coiled further from the corresponding magnetic pole. Consequently, the magnetic flux distribution that is generated by the winding group for one phase does not accurately follow a sine wave distribution, and adjustment will be required. Further, a winding group that is enlarged due to a large number of windings requires a wide spacing from the adjacent winding group. Therefore, the total number of magnetic poles is limited, and the number of phases is limited as well. Further, when the interval between adjacent winding groups is narrow, the use of the winding device becomes difficult.
In addition, when a winding is such that there is a gap between the beginning and end of the winding, as shown in FIG. 5, there is a tendency for the magnetic property and the output voltage to be skewed. Furthermore, with regard to FIG. 5, when the polarity of a magnetic pole is set to be opposite to that of the previous winding, the gap p makes it difficult to design, manufacture and adjust the winding with the proper number of turns.
When windings are not serially connected and magnetic poles are skipped but when there is a gap between the beginning and end of a winding for a magnetic pole is as in FIG. 5, the same problem that is described above occurs.